MAX6948B MAXIM [Maxim Integrated Products], MAX6948B Datasheet - Page 17

• Manufacturer Part Number: MAX6948B
• Description: High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports
• Manufacturer: MAXIM [Maxim Integrated Products]

Converter and Five Constant-Current GPIO Ports
Table 10. Input Ports Register Format (0x0E, Read Only)
Configure a port as a logic input by writing 0x01 to the
port’s output register (Table 7). Reading an input port
register returns the logic levels from the I/O ports config-
ured as a logic input (Table 10). The input port register
returns logic 0 in the appropriate bit position for a port
not configured as a logic input. The input ports’ registers
are read only. The MAX6948B ignores writes to the input
ports register.
Configuring all the ports as logic inputs or outputs (all
output registers set to value 0x00 or 0x01) or high imped-
ance (output register set to value 0xFF) puts the device
into standby mode. Put the MAX6948B into standby
mode for lowest supply current consumption.
Figure 3. Staggered Port and Boost PWM Waveform
REGISTER BIT
D7, D6, D5
D4
D3
D2
D1
D0
Standby Mode and Operating Current
42
High-Efficiency PWM LED Driver with Boost
PORT 0 OR PORTS AND BOOST IN PHASE
8.192ms NOMINAL PORT PWM PERIOD
84
PORT 2 STAGGERED PWM PERIOD
126
Ports Configured as Inputs
DESCRIPTION
PORT 3 STAGGERED PWM PERIOD
Reserved
168
P4
P3
P2
P1
P0
PORT 1 STAGGERED PWM PERIOD
210
PORT 4 STAGGERED PWM PERIOD
256
BOOST STAGGERED PWM PERIOD
PORT 0 OR PORTS AND BOOST IN PHASE
VALUE
NEXT PORT PWM PERIOD
0
0
1
0
1
0
1
0
1
0
1
PORT 2 STAGGERED PWM PERIOD
—
Port P4 is logic input low, or is not set as an input
Port P4 is logic input high
Port P3 is logic input low, or is not set as an input
Port P3 is logic input high
Port P2 is logic input low, or is not set as an input
Port P2 is logic input high
Port P1 is logic input low, or is not set as an input
Port P1 is logic input high
Port P0 is logic input low, or is not set as an input
Port P0 is logic input high
PORT 3 STAGGERED PWM PERIOD
Setting a port as a constant-current output increases the
operating current (output register set to a value between
0x02 and 0xFE), even if a load is not applied to the
port. The MAX6948B enables an internal current mirror
to provide the accurate constant-current sink. Enabling
the internal current mirror increases the device’s supply
current. Each output contains a gated mirror, which acti-
vates only when required.
In PWM mode, the current mirror turns on only for the
duration of the output’s on-time. This means that the
operating current varies as constant-current outputs are
turned on and off through the serial interface, as well as
by the PWM intensity control.
PORT 1 STAGGERED PWM PERIOD
PORT 4 STAGGERED PWM PERIOD
BOOST STAGGERED PWM PERIOD
PORT 0 OR PORTS AND BOOST IN PHASE
FUNCTION
NEXT PORT PWM PERIOD
PORT 2 STAGGERED PWM PERIOD
17